JPH06347494A - Resistance measuring device of armature and resistance measuring method using the device - Google Patents

Abstract

PURPOSE:To measure the connecting resistance between a winding and a commutator piece simply without cutting the winding of an armature, and to measure even a single winding resistance. CONSTITUTION:A constant current 1a is allowed to flow by making the first switch Sw1 ON, and the second switch Sw2 OFF, and the voltages Va1, Vb1, and Vc1 between neighboring commutator pieces C1 and C2, C2 and C3, and C9 and C10 are measured by voltage measuring devices 33, 34, and 35. Then, the generating voltages are controlled to make the voltage Vb2 measured by the voltage measuring device 34 equal to the voltage Vb1, by a voltage generator 32 making the ON and OFF of the switches Sw1 and Sw2 reverse, the voltages Va2 and Vc2 are measured again by the voltage measuring devices 33 and 35, and the connecting resistance RC1 of an armature 30 is calculated from the relational expression C1=(Va1-Va2)/1a, and the winding resistance RL1 is calculated from the relational expression RL1=Va2(Vc1+Vc2)/1a.Vc2, which are led by using the Ohm's law respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is for measuring the connection resistance between a winding (coil) of an armature (armature) and a commutator (commutator) in an electric motor (motor) and the winding resistance thereof. And a resistance measuring method using the same.

[0002]

2. Description of the Related Art Conventionally, the number of windings of an armature (rotor) used for an electric motor is measured by measuring the resistance value between all the commutator pieces of the commutator when all the windings are completed. It is confirmed whether or not the number of turns is a preset number of turns, or whether the winding (coil) is broken or there is no abnormality such as a short circuit between wires.

In the armature, the windings wound in the winding grooves of the core are respectively connected to the corresponding commutator pieces of the commutator, and the connection is spot welding which is advantageous in that automation can be achieved, for example. It is done in.

The spot welding is carried out by hanging a part of the winding wire on the outer peripheral surface of the commutator at a predetermined angle so that the locking end portion of each commutator piece does not sag, and then the engagement is performed. The toe is pressed against the outer peripheral surface of the commutator with the winding sandwiched, and the spot welding is performed to melt the coating of the winding (generally enamel wire), The copper wire portion is welded to the commutator piece to make it conductive.

If this spot welding is insufficient, when the armature is assembled to the stator (stator) and rotated as an electric motor, the engaging end of the commutator piece opens outward due to centrifugal force. Since the winding that should have been welded to it may come off, its management is extremely important. This welding state can be confirmed by measuring the connection resistance between the winding and the commutator piece.

However, since all the adjacent portions of the winding are connected to each other, it is difficult to accurately measure only the connection resistance of the portion to be measured. Since it is a very small value, for example, about 1/100 to 3/100 as compared with the resistance value of the winding wire, it was difficult to measure it accurately.

Therefore, the connection resistance value can be directly measured by cutting and taking out only the portion of the winding to be measured, but in such a case, it cannot be used as an armature. For the above reasons, it is ideal that the connection resistance between the armature winding and the commutator piece can be measured without cutting the coil. As a measuring method that realizes this, for example, Japanese Patent Laid-Open No. 61-29774. Some are described in Japanese Patent Publication.

The measuring method will be described with reference to FIG. In FIG. 2, 10 is an armature, and 6 windings each having a winding resistance of RB1, RB2, ..., RB6 are connected in a loop shape as shown in the drawing, and both ends of each winding constitute a commutator. Are connected to six commutator pieces 1, 2, ..., 6 respectively, and the connection resistances of the respective connection parts are RS1, RS2,
..., shown as RS6.

A first voltage generator 2 is provided between the commutator pieces 1 and 2.
The output voltage of 0 and the output voltage of the second voltage generator 21 are applied between the commutator pieces 2 and 3, respectively. Further, the voltages of the commutator pieces 4 and 6 are input to the control circuit 23, and the signal output from the control circuit 23 is input to the voltage regulator 22 according to the difference.

In the circuit thus constructed, the voltage V1 is applied between the commutator pieces 1 and 2, and the voltage V2 is applied between the commutator pieces 3 and 2, and the current I1 generated thereby is I2. Be larger than.

The current I1 is divided into two, one of which returns to the first voltage generator 20 through the connection resistance RS1 → the winding resistance RB1 → the connection resistance RS2, and the other of which becomes a current smaller than that current. , RS1 → RB6 → RB5 → RB4 → RB3 → RB2
-> Return to the first voltage generator 20 via RS2 (for convenience, only the sign of the resistor is shown).

Then, the voltage between the commutator pieces 4 and 6 is detected by the control circuit 23, and the voltage is set to zero to set the commutator pieces 4 and 6.
The voltage regulator 22 controls the voltage V2 generated by the voltage generator 32 so that the current does not flow during the period. In this way
The following equation is established by making the current flowing through the winding resistance RB6 and the connection resistance RS6 zero.

[0013]

## EQU1 ## RS1 = VX / I1 (VX is the voltage between commutator pieces 1 and 6)

[0014]

## EQU2 ## VY = RB1.I1 + RS2 (I1 + I2) (VY is the voltage between the commutator pieces 6 and 2)

Therefore, if the voltage VX and the current I1 are measured, the connection resistance RS1 can be obtained from the equation (1). Next, the armature 10 is rotated clockwise by one step (one segment) in FIG. 2 to move the connection resistance RS2 to the position where the connection resistance RS1 is located in FIG. Then, similarly to the case where the connection resistance RS1 is obtained by the above-described method, the connection resistance R
If S2 is calculated and voltage VY and current I2 are measured,
The winding resistance RB1 is obtained from Equation 2.

In this way, the armature 10 is rotated one step at a time, and the voltage and current are sequentially measured repeatedly, so that the connection resistance between all the commutator pieces and the windings and each commutator piece. The winding resistance between them can be obtained.

[0017]

However, in the case of the above-mentioned measuring method, the winding resistance between the commutator pieces of the armature is first determined by the connection resistance between one winding and the commutator piece. After measuring, the armature is rotated one stage, and the connection resistance between the winding and the commutator piece adjacent to it can be calculated only after measuring the winding resistance. It took time.

The present invention has been made in view of the above problems, and the connection resistance between the winding and the commutator piece can be easily measured without cutting the winding of the armature. The purpose is to do so. Another object of the present invention is to enable easy measurement in a short time without rotating the armature when measuring one winding resistance of the armature.

[0019]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a commutator having a plurality of commutator pieces provided on an armature, the first commutator piece and the third commutator piece and any of the following commutator pieces. Constant current generating means for flowing a constant current between the constant current generating means, a first switch for turning on / off the constant current by the constant current generating means, and two commutator elements after the third commutator element. A voltage generating means for applying a voltage between the two pieces, a second switch for turning on / off the voltage application by the voltage generating means, a first commutator piece and a second commutator piece adjacent to the first commutator piece. A first voltage measuring means for measuring a voltage between the two and a second voltage measuring means for measuring a voltage between adjacent two commutator pieces after the second commutator piece between the two commutator pieces connected to the constant current generating means. Second voltage measuring means, and a first switch with the first switch on and the second switch off. The generated voltage of the voltage generating means is set so that the voltage measured by the second voltage measuring means is the same in the switch switching position and the second switch switching position in which the first switch is off and the second switch is on. The voltage control means for controlling, the respective voltage measured by the first voltage measuring means at the first switch switching position and the second switch switching position, and the value of the constant current flowing by the constant current generating means are used to determine the armature. An armature resistance measuring device is configured by providing a connection resistance calculating means for calculating a connection resistance between the winding and the first commutator piece connected to the winding.

In the armature resistance measuring apparatus, the two adjacent commutator pieces located between the first commutator piece and one of the commutator pieces connected to the voltage generating means are closer to the first commutator piece. A third voltage measuring means for measuring the voltage between the two commutator pieces, a voltage measured by the third voltage measuring means at the first switch switching position, and a first voltage at the second switch switching position. From the respective voltages measured by the third voltage measuring means and the constant current flowing by the constant current generating means, the windings connected between the first commutator piece and the second commutator piece of the armature are Winding resistance calculation means for calculating the resistance may be provided.

Further, as a resistance measuring method using the armature resistance measuring device, the first and second switches are set to the first switch switching position, and the first rectifier of the commutator is rectified by the constant current generating means. A constant current is passed between the child piece and any commutator piece after the third commutator piece, and the voltage between the two adjacent commutator pieces is measured by the first and second voltage measuring means, Next, the first and second switches are set to the second switch switching position, and the voltage is applied between the two commutator pieces after the third commutator piece by the voltage generating means, and at that time, the second voltage is applied. After controlling the generated voltage of the voltage generating means such that the voltage measured by the measuring means becomes the same as the voltage measured at the first switch changeover position, the first voltage measuring means causes a gap between the adjacent commutator pieces. Again measure the voltage of
The armature winding is connected to the winding based on the voltage measured by the first voltage measuring means at this time, the voltage measured at the first switch switching position, and the value of the constant current passed by the constant current generating means. There is provided a resistance measuring method for calculating a connection resistance with the first commutator piece.

Further, as a resistance measuring method using the above-mentioned armature resistance measuring device provided with the above-mentioned third voltage measuring means and winding resistance calculating means, the first and second switches are replaced by the above-mentioned first and second switches. In the switch switching position of No. 1, a constant current is caused to flow between the first commutator piece of the commutator and any commutator piece after the third commutator piece by the constant current generating means, and each of the second and third commutator pieces. Each voltage between two adjacent commutator pieces is measured by the voltage measuring means, then the first and second switches are set to the second switch switching position, and the voltage generating means controls the voltage of the third commutator piece and thereafter. Generation of the voltage generating means such that a voltage is applied between the two commutator pieces, the voltage measured by the second voltage measuring means being the same as the voltage measured at the first switch switching position. After controlling the voltage, the first and third voltage measuring means are used. The voltage between the adjacent commutator pieces, and each voltage measured by the first and third voltage measuring means at this time, and measured by the third voltage measuring means at the first switch switching position. A resistance measuring method for calculating the resistance of the winding connected between the first commutator piece and the second commutator piece of the armature from the applied voltage and the value of the constant current passed by the constant current generating means. provide.

[0023]

According to the armature resistance measuring apparatus and the resistance measuring method using the apparatus according to the present invention, the first and second switches are set to the first switch switching position, and the constant current generating means controls the commutator. A voltage between two adjacent commutator pieces measured by the first voltage measuring means when a constant current is passed between the first commutator piece and any commutator piece after the third commutator piece; Next, the first and second switches are set to the second switch switching position, and the voltage is applied between the two commutator pieces after the third commutator piece by the voltage generating means, and at that time, the second voltage measurement is performed. After controlling the generated voltage of the voltage generating means such that the voltage measured by the means is the same as the voltage measured in the first switch position, the adjacent rectifiers measured again by the first voltage measuring means. The voltage between the child pieces and the constant current generating means From the value of the constant current, the contact resistance between the windings of the armature and the first commutator piece connect it can be obtained by calculation. Therefore, the connection resistance can be easily measured without cutting the armature winding.

According to the armature resistance measuring device provided with the above-mentioned third voltage measuring means and the winding resistance calculating means and the resistance measuring method using the device, the first and second switches are The third voltage is measured when a constant current is caused to flow between the first commutator piece of the commutator and an arbitrary commutator piece after the third commutator piece by the constant current generating means in the first switch switching position. The voltage between two adjacent commutator pieces measured by the means, and then the first and second switches are set to the second switch switching position, and the voltage generating means sets the second commutator piece and the second and subsequent ones.
A voltage is applied between the two commutator pieces, the generated voltage of the voltage generating means being such that the voltage measured by the second voltage measuring means is the same as the voltage measured at the first switch switching position. After controlling the voltage, the first commutator element of the armature is calculated from the voltage between the adjacent commutator elements measured by the first and third voltage measuring means and the value of the constant current passed by the constant current generating means. And the resistance of the winding connected between the second commutator element can be calculated. Therefore,
It is possible to easily measure in a short time without rotating the armature when measuring the resistance of one winding excluding the connection resistance in the armature.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic diagram for explaining an armature resistance measuring apparatus and a resistance measuring method using the apparatus according to the present invention.

In FIG. 1, reference numeral 30 denotes an armature, and ten windings each having a winding resistance of RL1, RL2, ..., RL10 are connected in a loop shape as shown in the drawing, and both ends of each winding are commutator. , 10 commutator pieces C1, C2, ...
, C10, and the connection resistances of the respective connection parts are shown as RC1, RC2, ..., RC10.

The resistance measuring device for this armature 30 is
Constant current generator 31, voltage generator 32 capable of controlling generated voltage, switch Sw1 (contact of relay CR1) and switch S for turning on / off a power supply circuit by these outputs
Controls w2 (contact point of relay CR2), first, second and third voltage measuring devices 33, 34 and 35, relays CR1 and CR2 and voltage generator 32, and measures first to third voltage. And a control calculation unit 40 for calculating the winding resistance and the connection resistance by inputting each measurement voltage from the devices 33 to 35.

Then, the constant current generator 31 connects the first commutator piece C1 and the third commutator piece C3 to any commutator piece (C4 in the illustrated example) through the switch Sw1 to provide a constant current. The voltage generator 32 includes two commutator pieces (C4 and C8 in the illustrated example) after the third commutator piece C3.
) Is applied to the voltage via the switch Sw2.

The switches Sw1 and Sw2 are connected to the relay CR1.
And CR2 according to a control signal from the control calculation unit 40, a first switch switching position in which the switch Sw1 is on and the switch Sw2 is off, and a switch Sw1 is off and Sw.
2 is controlled to a second switch position, which is on.

Further, the first voltage measuring device 33 measures the voltage between the commutator piece C1 and the commutator piece C2 adjacent to the commutator piece C1, and the second voltage measuring device 34 makes the above-mentioned commutator piece C1.
Between the second commutator piece C2 and the adjacent commutator pieces C2 and C3 between C2 and C4, the third voltage measuring device 3
5 is adjacent to each other and located between the first commutator piece C1 and the commutator piece C8 which is closer to the first commutator piece C1 among the commutator pieces C4 and C8 connected to the voltage generator 32. It is for measuring the voltage between two commutator strips (commutator strips C9 and C10 in the example shown).

The voltages Va, Vb and Vc respectively measured by the respective voltage measuring devices 33 to 35 are input to the control arithmetic unit 40.

The control calculation unit 40 includes a central processing unit (CPU) having various judgment and processing functions, and connection resistances Rc1 to Rc1 between the winding of the armature 30 and the commutator piece.
Rc10 and ROM, which is a program memory storing each program including an arithmetic program necessary for calculating the winding resistances RL1 to RL10, and fixed data (value of constant current Ia, etc.), and input data and processing data by the CPU It is possible to use a RAM, which is a data memory for temporarily storing the data, and a microcomputer configured by an input / output circuit (I / O) and the like.

In this embodiment, the control calculation section 40 controls the generated voltage of the voltage generator 32, the connection resistance calculation means for calculating the connection resistance, and the winding for calculating the resistance of the winding. Functions as a line resistance calculation means. Next, using the measuring apparatus configured as described above, the connection resistances RC1, RC2, ..., RC10 between the windings of the armature 30 and the commutator pieces C1 to C10, and the winding resistances RL1, RL2. ,,,
A method of measuring RL10 will be described.

As shown in FIG. 1, the armature 30 is set in the measuring device, the switch SW1 is turned ON, the switch SW2 is turned OFF (first switch switching position), and the constant current generator 31 sets a known constant. A current Ia is passed. In that state, the control calculator 40 controls the voltages Va1, Vb1 and Vc1 measured by the voltage measuring devices 33, 34 and 35, respectively.
To be stored in the internal memory.

Next, the switch SW1 is turned off and the switch SW2 is turned on (second switch switching position), and the voltage is applied by the voltage generator 32 to flow the current Ib.
At this time, the voltage Vb1 already measured by the voltage measuring device 34 and stored in the control arithmetic unit 40 and the current voltage measuring device 34
The control calculation unit 40 controls the voltage generated by the voltage generator 32 so that the voltage Vb2 measured by the same is the same (Vb1 = Vb2).

Then, in this state, the voltage measuring devices 33 and 35
The control calculation unit 40 calculates the voltages Va2 and Vc2 measured by
Stored in memory. At this time, the voltage Vc2 is stored as an absolute value. This completes the measurement for obtaining the connection resistance RC1 and the winding resistance RL1.

By the way, the voltage Va1 measured by the voltage measuring device 33 at the first switch switching position has a very large input impedance of the voltage measuring device 33, and therefore the current flowing through the commutator piece C2 is extremely small. Child piece C1
Considering the voltage between the point b and the point b in FIG. 1, almost no error occurs. Therefore, the voltage Va1 is obtained by the following equation (3).

[0038]

[Formula 3] Va1 = Ia · RC1 + Ia1 · RL1

The voltage Va2 measured by the voltage measuring device 33 at the second switch switching position is the same as the voltage measuring device 3
Since the input impedance of 3 is very large, the current flowing through the commutator pieces C1 and C2 is extremely small.
Considering the voltage between the point and the point b, there is almost no error. Therefore, at this time, the current flowing between a and b is Ib1
Then, the voltage Va2 is obtained by the following equation (4).

[0040]

[Equation 4] Va2 = Ib1 · RL1

On the other hand, when the voltages Va2 and Vc2 are measured as described above, Vb1 = Vb2 is set, so that Ia1 =
Ib1 is obtained, and from Equations 3 and 4, Ia.RC1 = Va1-Va2
Then, the following equation 5 is obtained.

[0042]

[Expression 5] RC1 = (Va1-Va2) / Ia

Therefore, according to this method, the connection resistance RC1 can be easily calculated from the equation (5) by the voltages Va1 and Va2 measured by the voltage measuring device 33 and the current Ia sent by the constant current generator 31. be able to.

In a similar manner, the armature 10 is rotated one stage (one segment), the connection resistance RC2 between the next adjacent commutator piece C2 and the winding is determined, and the connection resistance RC3 and thereafter are also calculated. We will seek in the same way.

Next, a method for measuring the winding resistances RL1 to RL10 between the commutator pieces of the armature 10 will be described. Figure 1
In the connection state shown in Fig. 4, when the first switch switching position is set, the voltage is measured by the voltage measuring device 35 and the control calculation unit 4
The voltage Vc1 stored in the memory of 0 is a relational expression of the equation 6 between the current Ia2 and the winding resistance RL9 when the current diverging from the point a in FIG. 1 to the winding resistance RL10 side at that time is the current Ia2. Holds.

[0046]

[Equation 6] Vc1 = Ia2 · RL9 RL9 = Vc1 / Ia2

Similarly, with respect to the voltage Vc2 measured by the voltage measuring device 35 when the second switch switching position is set, the relational expression of the equation 7 is established.

[0048]

[Formula 7] Vc2 = Ib1 · RL9 RL9 = Vc2 / Ib1

Since Ia1 = Ib1 as described above, RL9 = Vc2 / Ia1 and the following relational expression of Equation 8 can be obtained from Equation 1.

[0050]

[Formula 8] Vc1 / Ia2 = Vc2 / Ia1 Ia1 · Vc1 = Ia2 · Vc2

Further, since Ia = Ia1 + Ia2, the relational expression is as shown by the equation 9, and the current Ia1 can be obtained.

[0052]

[Formula 9] Ia1 · Vc1 = (Ia−Ia1) Vc2 = Ia · Vc2-Ia1 · Vc2 Ia1 · Vc1 + Ia1 · Vc2 = Ia · Vc2 Ia1 (Vc1 + Vc2) = Ia · Vc2 ∴Ia1 + Ia2 / Vc2

Since RL1 = Va2 / Ia1, Mathematical expression 10 is obtained by substituting the above equation into Ia1.

[0054]

RLl = Va2 / {Ia.Vc2 / (Vc1 + Vc2)} = Va2 (Vc1 + Vc2) /Ia.Vc2

Therefore, the measurement is already performed and the control calculation unit 40 is
The winding resistance RL1 can be easily obtained by performing the operation of the equation (10) with the respective voltages Va2, Vc1, Vc2 stored in the memory and the current Ia supplied by the constant current generator 31.

In a similar manner, the armature 3 also applies to the adjacent winding resistance RL2 and the winding resistances RL3 to RL10 thereafter.
While rotating 0 for one step (one segment), repeat the same measurement for the number of commutator segments.

As described above, this measuring method does not include the connection resistance between the armature winding and each commutator piece, and the winding resistance other than the connection resistance between each commutator piece. This is convenient because it is possible to easily measure one winding resistance and to measure the one winding resistance without rotating the armature.

[0058]

As described above, according to the resistance measuring apparatus for an armature according to the present invention, the first and second switches are set to the first switch switching position by carrying out the above resistance measuring method. From each voltage between the two adjacent commutator pieces measured by the first voltage measuring means and the value of the constant current flowing by the constant current generating means when the armature is moved to the second switch switching position, The connection resistance between the winding and the first commutator piece connecting the winding can be calculated. Therefore, without cutting the armature winding,
The connection resistance can be easily measured.

Further, according to the resistance measuring device of the armature provided with the third voltage measuring means and the winding resistance calculating means, by carrying out the above-mentioned resistance measuring method using the device, The voltage between the adjacent commutator segments measured by the third voltage measuring means when the second switch is in the first switch switching position, and the first and second voltages when the switches are in the second switch switching position. The first commutator segment of the armature and the second commutator segment of the armature are calculated from the respective voltages measured by the third voltage measuring means and the value of the constant current passed by the constant current generating means.
One winding resistance connected between the commutator piece and the commutator piece can be calculated. Therefore, when measuring one winding resistance between each commutator piece of an armature, it can be easily measured in a short time without rotating the armature.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an armature resistance measuring apparatus and a resistance measuring method using the apparatus according to the present invention.

FIG. 2 is a schematic diagram for explaining an example of a conventional resistance measuring method capable of measuring a connection resistance between an armature winding and a commutator piece without cutting a winding.

[Explanation of symbols]

 30 armature 31 constant current generator 32 voltage generator 33, 34, 35 voltage measuring device 40 control arithmetic unit C1 to C10 commutator piece Sw1, Sw2 switch

Claims (4)

[Claims] 1. A constant current generator for supplying a constant current between a first commutator piece of a commutator having a plurality of commutator pieces provided on an armature and an arbitrary commutator piece after the third commutator piece. Means, a first switch for turning on / off a constant current by the constant current generating means, a voltage generating means for applying a voltage between two commutator pieces subsequent to the third commutator piece, A second switch for turning on / off the voltage applied by the voltage generating means; and a first voltage measuring means for measuring a voltage between the first commutator piece and a second commutator piece adjacent thereto. Second voltage measuring means for measuring a voltage between adjacent commutator pieces after the second commutator piece between two commutator pieces connected to the constant current generating means, and the first switch. Is turned on and the second switch is turned off, and the first switch switching position and the first switch are turned on. Voltage control means for controlling the generated voltage of the voltage generating means so that the voltages measured by the second voltage measuring means become the same at the second switch switching position where the switch is turned off and the second switch is turned on. The armature winding from the respective voltages measured by the first voltage measuring means at the first switch switching position and the second switch switching position and the value of the constant current flowing by the constant current generating means. An armature resistance measuring device comprising: a connection resistance calculating means for calculating a connection resistance between a wire and the first commutator piece connected to the wire. 2. The armature resistance measuring device according to claim 1, between the first commutator piece and one of the commutator pieces connected to the voltage generating means, which is closer to the first commutator piece. For measuring the voltage between two adjacent commutator strips located at
Voltage measuring means, the voltage measured by the third voltage measuring means at the first switch switching position, and the voltage measured by the first and third voltage measuring means at the second switch switching position. Winding resistance calculation for calculating the resistance of the winding connected between the first commutator segment and the second commutator segment of the armature from each voltage and the constant current generated by the constant current generating unit. An armature resistance measuring device comprising: 3. A resistance measuring method using the armature resistance measuring device according to claim 1, wherein the first and second switches are set to the first switch switching position, and the constant current generating means. By the first of the commutator
A constant current is caused to flow between the commutator piece and any commutator piece after the third commutator piece, and the voltage between the two adjacent commutator pieces is measured by the first and second voltage measuring means. Then, the first and second switches are set to the second switch switching position, and a voltage is applied between the two commutator pieces subsequent to the third commutator piece by the voltage generating means. And controlling the voltage generated by the voltage generating means so that the voltage measured by the second voltage measuring means becomes the same as the voltage measured at the first switch switching position, and then the first voltage The voltage between the adjacent commutator pieces is measured again by the measuring means, and the voltage measured at this time by the first voltage measuring means and the voltage measured at the first switch switching position and the constant current generation. From the value of the constant current flowed by the means Resistance measurement method characterized by calculating the connection resistance of the armature winding and the first commutator piece connect it. 4. A resistance measuring method using the armature resistance measuring apparatus according to claim 2, wherein the first and second switches are set to the first switch switching position, and the constant current generating means is used. A constant current is caused to flow between the first commutator piece of the commutator and an arbitrary commutator piece after the third commutator piece, and the two adjacent rectifiers are respectively made by the second and third voltage measuring means. Each voltage between the armature pieces is measured, then the first and second switches are set to the second switch switching position, and the voltage generating means is used to connect the two commutator pieces after the third commutator piece. Voltage is applied to the second voltage measuring means, and the voltage generated by the voltage generating means is controlled so that the voltage measured by the second voltage measuring means is the same as the voltage measured at the first switch switching position. After that, by the first and third voltage measuring means The voltages between the adjacent commutator pieces are measured, and the respective voltages measured by the first and third voltage measuring means at this time and the third voltage measurement at the first switch switching position are measured. The resistance of the winding connected between the first commutator segment and the second commutator segment of the armature is calculated from the voltage measured by the means and the value of the constant current passed by the constant current generating means. A method of measuring resistance, comprising: